In that case Johto or Unova would be the best candidates as Sinnoh,Hoenn, and Kanto are fairly large. I think if anything it'll be Unova to Parallel generation 2's trip to Kanto. Maybe if the add the original Dragon they could have it's event there. Yet again if they had Unova in 3D one would ask why they didn't make B2W2 3D, unless they didn't have enough time.